1. Field of the Invention
The present invention relates to a speaker apparatus used for audio reproduction and so on.
Further, the present invention relates to a supporting apparatus which supports a speaker apparatus or the like so that the speaker apparatus is positioned away from a floor surface or the like, and which enables changing of facing direction of the speaker apparatus.
Further, the present invention relates to a speaker structure, more specifically, relates to a speaker structure comprising a speaker unit in which a through hole is formed in a magnetic circuit portion.
2. Description of the Related Art
Since before, a speaker apparatus capable of sound reproduction of high sound quality in a wide frequency band has been demanded in audio reproduction. In order to extend a frequency band toward low-pitched sounds, it is necessary to use a speaker apparatus in which a speaker of large caliber is placed in a speaker box having a large capacity. In a speaker, acoustic vibrations are propagated to the surrounding air from a vibration board driven to vibrate by a driving portion of, for example, electrodynamic type provided with a magnetic circuit and a voice coil. A reaction force from the surrounding air is transmitted to the vibration board, and the driving portion also vibrates in response to the acoustic vibrations propagated to the air. These vibrations are transmitted to the speaker box, whereby the surface of the speaker box vibrates, and acoustic output by these vibrations is also radiated to the surrounding air. Since this acoustic output contains a phase shift and distortion as compared with acoustic output radiated from the vibration board, the sound quality of acoustic output radiated from the speaker degrades.
Further, in many cases, a speaker of large caliber for low-pitched sounds is installed in a speaker box having a large capacity, and a speaker of small caliber for high-pitched sounds is disposed independently from the speaker for low-pitched sounds. The applicant disclosed a speaker system in which a speaker box having a relatively small capacity can be divided into a first half portion and a second half portion, an opening portion is disposed to the first half portion to connect a sound radiation portion of a full-range speaker unit of relatively small caliber via a cushioning material, and the speaker unit is supported inside the speaker box (refer to Japanese Unexamined Patent Publication JP-A 2001-285974 (FIGS. 1 and 17), for example). The speaker unit is directly supported by a stand whose front end is inserted into the speaker box from a connecting portion between the first half portion and the second half portion of the speaker box, whereby vibrations occurring in, for example, a driving portion of the speaker unit is hard to propagate to the speaker box.
In the speaker system as disclosed in JP-A 2001-285974 (FIGS. 1, 17), the front end of the stand outside the speaker box is inserted into the speaker box to support the speaker unit. Since the cushioning material or the like is disposed to a place where the stand is inserted into the speaker box so that acoustic output inside the speaker box does not leak outside, it is impossible to cause the speaker box to swing on the stand. In the case of reproduction of high-pitched sounds, the directivity is strong for acoustic output radiated from the speaker. In the case of executing stereo reproduction by placing the speaker system in spatially separate positions, for example, on the right side and the left side, it is preferable to direct the speaker system toward a listener.
FIG. 26 schematically shows a supporting structure 50 which enables a swing. A spherical body 52 is installed in a supporting object 51, and the spherical body 52 is covered by a shell member 54 having a groove into which a shaft 53 extending outward in a radial direction from a part of the spherical body pierces and the shell member 54 is fixed by a bolt 55. With the bolt 55 slightly loosened, an angular displacement about the shaft 53 and a swing displacement of the shaft 53 along the groove become possible in the supporting structure 50. It is possible fix the direction of the shaft 53 by fasten the bolt 55 when the shaft 53 is set in a desired direction.
In the case of using the supporting structure 50 as shown in FIG. 26 in a speaker system, it is necessary to house an approximately half portion of the spherical body 52 into the speaker box as the supporting object 51. Since the speaker system has a weight even if relatively small, the diameter of the spherical body 52 must be large to a certain extent. As the spherical body 52 becomes large, the capacity of the speaker box becomes small because the speaker box houses the half portion of the spherical body.
FIG. 27 shows a state where the major portion of the spherical body 52 is put outside the supporting object 51 in order to avoid that the capacity of the sneaker box becomes small. However, in this case, the spherical body 52 and the supporting object 51 tend to become unstable because a contact area thereof is small. Moreover, since the major portion of the spherical body 52 is put outside the supporting object 51, a height h of the supporting structure becomes large.
FIG. 28 is a sectional side view schematically showing a conventional speaker structure.
A speaker unit 100 comprises a magnetic circuit portion 120, a vibrating portion 130 and a frame 140. The magnetic circuit portion 120 includes a yoke 121 made of a magnetic substance such as iron, an annular magnet 122 placed on a front face side of the yoke 121, and an annular top plate 123 placed on the front face side of the magnet 122. The yoke 121 is composed of a columnar center pole 121a and a back plate 121b, and a through hole 124 for air bleed is formed on the central axis of the center pole 121a. Moreover, the magnet 122 is placed in a manner that the central axis of the magnet 122 coincides with the central axis of the center pole 121a. 
The vibrating portion 130 includes a cone 131 having a substantially truncated cone shape, an edge 132 adhered and fixed to one end on a front face side of the cone 131, a cylindrical voice coil bobbin 133 adhered and fixed to another end on a rear side of the cone 131, a voice coil 139 wound around an outer periphery of the voice coil bobbin 133, an annular damper 135 adhered and fixed to the voice coil bobbin 133 and the frame 140, a center cap 136 for capping a central portion of the cone 131, and the like.
The frame 140 is a member for fixing the magnetic circuit portion 120 and the vibrating portion 130, and is formed in a substantially truncated cone shape. A front opening portion of the frame 140 is adhered and fixed to the cone 131 via the edge 132. A rear portion of the frame 140 is adhered and fixed to the top plate 123 of the magnetic circuit portion 120. A hole (not shown) for regulating back pressure of the cone 131 is formed in a predetermined position on a sidewall surface of the frame 140.
When the voice coil 134 of the speaker unit 100 is energized, a driving force acts on the voice coil 134 in a magnetic gap, the cone 131 displaces, and sound waves are radiated from the cone 131 to the surroundings. At this moment, the voice coil 134 generates heat, and this heat is radiated from a gap between the top plate 123 and the center pole 121a to an interior space 141 of the speaker unit 100, and transmitted to the respective members such as the yoke 121.
According to the speaker unit 100, since the through hole 124 is formed in the yoke 121, the high-temperature air is discharged from the interior space 141 to a back face side via the through hole 124 when the cone 131 is pressed backward, and the outside air is sucked into the interior space 141 from the back face side via the through hole 124 when the cone 131 is drawn back forward. As a result, it is possible to increase a heat radiation characteristic of the interior space 141, and it is possible to increase the cooling efficiency of the yoke 121.
FIG. 29 is a sectional side view schematically showing another conventional speaker structure. Here, since a speaker unit 100A is almost the same as the speaker unit 100 shown in FIG. 29 except that a screw hole 250 with a screw thread cut is formed instead of the through hole 124 for air bleed formed in the yoke 121, a yoke and the screw hole will be denoted by different reference numerals 210 and 250, respectively, and the other components having the same functions will be denoted by the same reference numerals and and a description thereof will be omitted.
A speaker apparatus 101 comprises the speaker unit 100A and a weight 150 fixed on the back face side of the speaker unit 10A.
A main body portion 151 of the weight 150 is made of metal having a high specific gravity such as iron, stainless steel and lead, and has a larger weight than that of the speaker unit 100A.
A front face of the main body portion 151 having a substantially truncated cone shape is formed by a plane surface except a protruding port-on 152 in the center, and a through hole 153 for inserting a bolt 160 is formed along the central axis of the main body portion 151.
The speaker unit 100A and the weight 150 are combined by inserting the bolt 160 into the through hole 153 from the back face side of the weight 150, and inserting and screwing a front end portion of the bolt 160 protruded from the protruding portion 152 of the weight 150 into the screw hole 250 disposed to the back face of the yoke 210.
According to the speaker apparatus 101, since the weight 150 is fixed on the back face side of the magnetic circuit portion 120 of the speaker unit 100A, even if a reaction force occurring at the time of radiation of sound waves from the cone 131 transmits to the magnetic circuit portion 120, the weight 150 works as a virtual ground, with the result that vibrations are suppressed, and a sound quality with fine transient characteristic can be obtained (refer to Japanese Unexamined Patent Publication JP-A 2002-152884).
FIG. 30 is a sectional side view schematically showing a conventional two-way type of speaker structure. Here, components having the same functions as those of the speaker unit 100 shown in FIG. 28 will be denoted by the same reference numerals and a description thereof will be omitted.
A speaker unit 101A comprises a main speaker unit 110 having the magnetic circuit portion 120, the vibrating portion 130 and the frame 140, a center support 170 fixed on the front face side of the center pole 121a of the magnetic circuit portion 120, and a tweeter unit 112 adhered and fixed on the front face side of the center support 170.
A through hole 250A for inserting a bolt 160A is formed along the central axis of the magnetic circuit portion 120 (the center pole 121a) of the main speaker unit 110. Moreover, a screw hole 171 for screwing the bolt 160A is formed in the center support 170 made of a nonmagnetic substance (resin, aluminum, stainless steel or the like).
The tweeter unit 112 is a speaker for high audio frequencies, and includes a magnetic circuit portion, a vibrating portion and a frame, which are not shown in the drawings.
The main speaker unit 110 and the center support 170 are combined by inserting the bolt 160A into the through hole 250A from the back face side of the magnetic circuit portion 120, and inserting and screwing a front end portion of the bolt 160A protruded from the through hole 250A into the screw hole 171 of the center support 170.
By a structure such that the tweeter unit 112 for high audio frequencies is attached to the main speaker unit 110 for medium and low audio frequencies, it is possible to output sounds of a wide band from low-pitched sounds to high-pitched sounds by the single speaker apparatus 101A. Such a two-way type of speaker structure is disclosed in, for example, Japanese Unexamined Patent Publication JP-A 2002-209293.
However, even if intending to attach the weight 150 shown in FIG. 29 to the speaker unit 100 having the through hole 124 for air bleed shown in FIG. 28, it is impossible to attach the weight 150 as it is because the through hole 124 is formed in the speaker unit 100. Moreover, although it is possible to attach by cutting a screw thread in the through hole 124 when the diameter of the bolt 160 is larger than the hole diameter of the through hole 124, the through hole 124 is filled with the bolt 160 when the bolt 160 is attached to the through hole 124, and therefore, there is a problem such that it is impossible to obtain an effect of air bleed by the through hole 124, that is, an effect of increasing the cooling efficiency of the magnetic circuit portion 120 by suck and discharge of the air.
Further, since the through hole 250A is filled with the bolt 160A in the two-way type of speaker apparatus 101A shown in FIG. 30, it is impossible to execute air bleed, and there is a problem such that the efficiency of heat radiation of the magnetic circuit portion 120 cannot be increased.